Refueling stations for vehicles may have fuel dispenser pumps that dispense gasoline (or a gasoline fuel blend) or diesel fuel, to accommodate vehicles that run off of either fuel type. However, if diesel fuel is unknowingly introduced into a gasoline engine, engine parts may be damaged. For example, due to diesel fuel being heavier than gasoline, the introduction of diesel fuel into a gasoline engine may result in clogging of fuel injectors. In addition, the misfueling can result in spontaneous ignition of the diesel fuel inside gasoline engine cylinders. This can result in high costs associated with repairing and replacing engine components. In addition to costs associated with draining out the diesel fuel and flushing fuel system components such as the fuel pump, fuel filter, and fuel injectors.
To discourage the introduction of diesel fuel into gasoline engines (or vice versa), many gas stations include refueling nozzles that differ for gasoline compared to diesel fuel. For example, gasoline dispenser nozzles may differ from diesel nozzles in diameter, such that nozzles designed for diesel fuel do not readily fit into a fuel filler neck of a gasoline engine. In still other examples, dispenser nozzles may additionally or alternatively be color coded, to clearly demarcate to a dispenser operator which nozzles are for gasoline as compared to diesel fuel. However, there may be refueling stations where a similar nozzle diameter and color is used for both diesel and gasoline fuels, increasing the likelihood of potential misfueling of a vehicle fuel tank. Accordingly, various approaches have been developed for detecting and mitigating further misfueling.
One example approach for detecting misfueling is shown by Zerangue et al. in US 20030209280. Therein, once a fuel nozzle is inserted into the filler neck, a vacuum pump is activated to create a seal around the fuel nozzle. The type of dispensed fuel is then identified via a sensing unit by measuring the dispensed fuel vapor pressure and comparing it to predetermined vapor pressure values. If misfueling is detected, the sensing unit actuates a valve, which is affixed across the filler neck passageway, to a closed position. Once the valve is closed, the backpressure in the fuel tank increases which engages the fuel pump's internal shut-off mechanism, disabling any more of the incorrect fuel from being dispensed into the fuel tank.
However, the inventors herein have recognized potential issues with such an approach. Specifically, there may be markets where the installation of a sensing unit to identify fuel based on vapor pressure (e.g. Fuel Tank Pressure Transducer (FTPT) sensor) is not required, such as in most countries in Europe and Asia (e.g. China and India). Furthermore, the addition of a vacuum pump (coupled to the sensing unit) in the refueling system may add significant component cost.
The inventors herein have recognized that the differences in fuel pressure between gasoline and diesel may lead to different rates of vapor adsorption in a carbon canister coupled to the fuel tank. In particular, gasoline, which is more volatile than diesel due to the presence of shorter chain hydrocarbons, may evaporate more rapidly than diesel in response to diurnal variations in ambient temperature. Due to the higher evaporation rate, during a refueling event with gasoline, a larger amount of fuel vapors are adsorbed in the carbon canister. The exothermic reaction associated with vapor adsorption in the canister results in an increase in canister temperature. In comparison, due to the lower evaporation rate, during a refueling event with diesel, a smaller amount of fuel vapors are adsorbed in the carbon canister, resulting in a negligible exothermic reaction. Therefore a temperature gain of the carbon canister during a refueling event may be advantageously used for inferring misfueling.
In one example, misfueling may be timely detected and addressed by a method, comprising: responsive to misfueling of a fuel tank identified based on an actual temperature profile at a fuel system canister during a refueling event relative to an expected temperature profile, the expected temperature profile based on a fuel level in the fuel tank, disabling further addition of fuel during the refueling event. In this way, misfueling may be promptly detected, and further filling of a fuel tank with an incorrect fuel may be averted.
As an example, during refueling, an actual fuel level in a fuel tank may be monitored via a fuel level sensor and an expected temperature gain in a fuel vapor canister coupled to the fuel tank may be estimated based on the fuel level and the expected fuel type. For example, when the expected fuel in the fuel tank is gasoline, an expected temperature gain of the canister may be calculated based on the fuel level and the evaporation rate (or volatility) of gasoline. An actual temperature gain is then determined via a temperature sensor coupled to the canister, such as one or more thermocouples positioned at different locations inside the canister. Based on the actual temperature gain being lower than the expected temperature gain, misfueling may be inferred. For example, it may be inferred that the fuel tank is being incorrectly filled with a lower volatility fuel, such as diesel. In response to the indication of misfueling, a fuel tank isolation valve may be commanded closed to actively raise a filler pipe pressure and induce a shut off of the refueling dispenser, thereby mitigating the further addition of the incorrect fuel type to the fuel tank. Furthermore, the vehicle operator may be alerted that misfueling has occurred so that appropriate mitigating actions may be taken.
In this way, misfueling may be detected based on a temperature change within a fuel vapor canister during a refueling event. By relying on the effect of adsorbed fuel vapors on a temperature gain at the canister, temperature changes in the fuel vapor canister during refueling may be correlated with the presence of an incorrect fuel (e.g., a fuel having a different volatility than the expected fuel) in the fuel tank while using existing temperature sensors. By relying on inexpensive canister temperature sensors (or thermocouples), misfueling may be detected in a more cost-effective manner, with reduced reliance on expensive and bulky hardware such as vacuum pumps. By sealing the fuel tank responsive to the indication of misfueling, further addition of the incorrect fuel into the fuel tank is pre-empted.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.